Casing joint

ABSTRACT

A gas turbine engine casing is joined at circumferential split lines by coupling members formed as rings having flanges which interlock with flanges on the casing sections to hold them against separation and having flanges which are deformed to bear directly or indirectly against the outer surface of the casing to hold the first flanges in engagement. The coupling ring as provided includes a third flange which provides an abutment or reaction surface for a tool which deforms the second flange. A heat shield may be provided on the coupling ring. If a gap between the ends of the ring is necessary for fitting, this is closed by a plug or key on which an internal head is formed by exertion of radial force. The flange on the ring or key against which the force reacts may be removed after the joint is completed. The same sort of joint may be provided at axial or other split lines. The deformed flanges may be pressed against teeth on the casing sections to provide a positive anti-torque connection.

United States Patent Johnson 15] 3,655,223 [4 1 Apr. 11, 1972 [73]Assignee: General Motors Corporation, Detroit,

Mich.

221 Filed: Sept. 17,1969

21 Appl.No.: 858,698

[52] U.S. Cl ..285/39, 285/187, 285/328, 285/382, 285/398, 285/407,285/422 [51] Int. Cl ..F16l35/00 [58] Field of Search ..285/39, 187,330, 364, 365, 285/366, 367, 371, 407, 408, 409, 410, 411,420,302:287/l89.366.1l1.1l8

[56] References Cited UNITED STATES PATENTS 665,003 1/1901 Haigh..285/382.2 831,551 9/1906 Guttzeit ..285/41l X 880,507 3/1908 Cook..285/398 X 2,601,995 7/1952 Skopil ..285/364 X 2,673,659 3/1954 Moore.....287/l89.366 2,759,574 8/1956 Miller ..287/189.366 3.529.855 9/1970Bragg ..285/398 X FOREIGN PATENTS OR APPLlCATlONS 882,501 11/1961GreatBritain ..285/407 547,628 9/1956 Italy ..285/366 PrimaryExaminer-Dave W. Arola Attorney-Paul Fitzpatrick and Jean L. Carpenter57 ABSTRACT A gas turbine engine casing is joined at circumferentialsplit lines by coupling members formed as rings having flanges whichinterlock with flanges on the casing sections to hold them againstseparation and having flanges which are deformed to bear directly orindirectly against the outer surface of the casing to hold the firstflanges in engagement. The coupling ring as provided includes a thirdflange which provides an abutment or reaction surface for a tool whichdeforms the second flange. A heat shield may be provided on the couplingring. If a gap between the ends of the ring is necessary for fitting,this is closed by a plug or key on which an internal head is formed byexertion of radial force. The flange on the ring or key against whichthe force reacts may be removed after the joint is completed. The samesort of joint may be provided at axial or other split lines. Thedeformed flanges may be pressed against teeth on the casing sections toprovide a positive anti-torque connection.

29 Claims, 10 Drawing Figures k w A9 Patented A ril 11, 1912 3,655,223

2'Sheets-Sheat l flay/as J /mson 2 Sheets-Shoot 1:

Patented April 11, 1972 4690a /as c/Z/mson BY CASING JOINT The inventionherein described was made in the course of work under a contract orsubcontract thereunder with the De partment of Defense.

DESCRIPTION My invention is directed to joints between parts of walls orcasings of various sorts, particularly those which contain a fluid underpressure such as pressure vessels, gas ducting, and the casings of gasturbine engines. The invention is particularly suitable to provide alightweight, strong, rigid, readily applied joint between adjacentsections of the outer casing of a gas turbine engine, for example, andis so described herein. However, as will be apparent to those skilled inthe art, the principles of my casing joint are applicable to varioussituations.

Particularly with reference to the casings of aircraft gas turbines, jetengine exhaust pipes, and the like, there is a need for structures whichare as light in weight as possible but which are capable of withstandingsubstantial separating forces as well as vibrations, high temperature,and other adverse conditions. In turbojet lift engines, the minimizationof unnecessary weight is particularly vital. In other applications theweight problem in casing joints may not be so acute, but it is stillpresent, and as far as I am aware there has not yet been a solution tothis problem which has been generally considered satisfactory.

It will be appreciated that separating forces in the casings of gasturbine engines of normal or large size due to the pressure of containedgas are quite substantial. The conventional approach to joining casingsections lies in providing flanges along circumferential or axial splitlines which are coupled by through bolts and nuts. For circumferentialjoints, another approach has been the use of a circumferentiallytensioned ring embracing flanges on the casing sections. A lessconventional approach to the problem is disclosed in US. Pat. No.3,014,741 of C. J. McDowall for Multimember Joints. All of theseexpedients result in joints which are bulkier, heavier, and usually moredifficult to machine and assemble than the joint arrangement which isthe subject of my invention.

According to the preferred embodiment of my invention, the two parts tobe joined have juxtaposed edges with flanges on one surface definingabutments spacing away from each other and abutments on the othersurface facing toward each other. The abutments which face away fromeach other are coupled by recurved flanges on a coupling strip or ringwhich includes deformable flanges which directly or indirectly engagethe other surface of the casing section. The recurved flanges hold theparts together against forces tending to separate them and theengagement with the abutments which face together holds them securelyapart, preventing any rattle or shake in the joint when the pressure isnot present. The coupling ring or strip includes a removable flangewhich provides a reaction surface for a forming tool which deforms theplastic flange to secure the connecting joint member and may thereafterbe removed. The result is a strong, lightweight, compact, positive,relatively leakproof, semi-permanent joint which, however, may be takenapart by machining away parts of the coupling ring.

The nature of my invention and its advantages will be clear to thoseskilled in the art from the succeeding detailed description of preferredembodiments of the invention and the accompanying drawings thereof.

FIG. 1 is a fragmentary view of the casing of a turbojet engine taken ina plane containing the axis of rotation of the turbine and illustratingtwo applications of easing joints according to the invention.

FIG. 2 is a cross-section of a joint which may be an enlarged view of aportion of FIG. 1.

FIG. 3 is a view corresponding to FIG. 2 illustrating a step in theformation of the joint.

FIG. 4 is a view similar to FIG. 2 illustrating a modified form of jointstructure.

FIG. 5 is an enlarged transverse sectional view on the plane indicatedby the line 5-5'in FIG. 1, with curvature exaggerated.

FIG. 6 is a sectional view through a sealing key employed between theends of the coupling ring taken on the plane indicated by the line 6-6in FIG. 5.

FIG. 7 is an axonometric view of the sealing key before insertion.

FIG. 8 is a sectional view of a casing joint with an antitorque lock,before deforming.

FIG. 9 is a similar view after deforming.

FIG. 10 is a fragmentary cross-sectional view taken on the planeindicated by the line 10-10 in FIG. 9.

Referring first to FIG. 1, a turbojet engine 9 includes a first casingsection 10, a second casing section 11, and a third casing section 12,these three defining a portion of the outer wall of an engine which maybe of conventional type. The casing contains gas under pressure whichflows through the engine and therefore may be considered as exemplary ofa pressure vessel or duct for gas under pressure as well as exemplary ofan engine outer case. Sections 10 and 11 are joined together by acoupling member or coupling ring 14 and sections 11 and 12 by a couplingring arrangement 15 which is illustrated in course of application tosections 11 and 12. The casing sections 11 and 12 are double walled, theformer having an outer wall 16 and an inner wall 18, and the latterincluding an outer wall 19 and an inner wall 20. The space between thewalls may be a conduit for cooling air.

A ring of turbine nozzle vanes 22 extends inwardly from the casingsection 11 and blades 23 of a turbine wheel rotate inside the casingsection. Struts 24 extend inwardly from the casing section 12 to supporta turbine bearing or inner tailcone of the engine. The turbine issupplied by a combustion apparatus defined in part by wall 26 mountedwithin the section 10. Details of such an engine are immaterial to thisinvention; however, for purposes of illustration, mention may be made ofmy prior US. Pat. Nos. 3,286,461 for Turbine Starter and Cooling and3,332,242 for Aft Fan Jet Engine which disclose more fully structures ofengines of the general type to which reference is made in FIG. 1.

One example of a casing joint according to my invention is shown moreclearly in FIG. 2 which shows joint 15 between the engine casingsections 11 and 12, or any other joint of similar structure.

The meeting planes of casing sections such as at 14 and 15 are commonlyreferred to in the art as split lines. The split lines illustrated arecircumferential lines, but the term applies also to longitudinal casingjoints, and the invention is applicable to casing joints howeveroriented. However, the application to circumferential joints may besomewhat more difficult than to an axial joint, so that circumferentialjoints are emphasized in this disclosure to explain the principles ofthe invention.

Referring to F IG. 2, it will be noted that the adjacent ends of thecasing sections or walls 11 and 12 are juxtaposed, being spaced slightlyapart. These casing sections bear inwardly directed flanges 27 the rearsurfaces of which define abutments 28 directed away from the adjacentshell, these abutments being radial or, more generally, being directedapproximately perpendicularly to the surface of the casing or shell. Theends of the casing section also are chamfered on the outer surface asindicated at 30, these chamfers defining abutments facing toward theadjacent casing section.

The coupling member 15 of FIG. 2 is a 360 metal ring with a single splitwhich provides a gap in the ring so that it may be fitted into place byradial expansion. The coupling member 15 has a radially extending webmade up of two parts, an inner ring 31 and an outer ring 32, these beingjoined together by an annular weld or other suitable bond at 34. Thereason for this bimetallic structure is that the inner portion of thering performs the duty of holding the casing sections together againstthe pressures exerted on them and, in the illustrated case, also needsto be a high temperature resisting material. In this particular example,the inner ring is Inco 718, high temperature resisting material of lowductility which cannot be cold formed after heat treatment. The outerportion of the ring is of 347 stainless steel which is less temperatureresisting and which is ductile. The need for the ductility will be madeapparent.

The high temperature resisting portion of the ring includes alignedconnecting flanges 35 extending from both faces of the web, theseflanges being recurved so as position, define a radial shoulder 36 whichabuts the corresponding abutment 28 when the parts assembled. Tension inthe case is thus taken from the first abutment 36 through shoulder 28and the flanges 35 to the second abutment 36 and shoulder 28. Since thering is split, it may be overlapped so as to fit into the casing pastthe flanges 27 and then may be expanded outwardly to the position shown,in which it bears against the radially inner surface of the casing. Thecoupling ring is retained in this position by means bearing against theouter surface of the casing, which, in the preferred structure, alsobiases the casing sections apart so that there is no lost motion betweenthe parts when they are not held apart by the contained pressure.

In the structure shown in FIG. 2, the means for retaining the couplingring in active position comprises ductile flanges 38 extending from bothfaces of the web portion 32. The outer portion of the ring also includesan outer ring or abutment 39, of considerably more massive structurethan the flanges 38, which defines a flange or head 40 extending fromeach face of the web 32 overlying the flanges 38. The operative parts ofthe casing joint of FIG. 2 are completed by two filler rings 42 disposedbetween the flanges 38 and the abutments,

of the casing sections and bearing against the web 31, 32. The fillerring or strip 42 may be, and in many cases preferably is, made up of anumber of segments but it is immaterial to the operative character ofthe filler strip whether or not it is segmented. The purpose of thefiller strip 42 is to act as a wedge to transmit force from the ductileflanges 38 to the case and to provide a clearance for the flanges of thecoupling member to clear the flanges 27 of the case in assembly.

The strips 42 preferably have rounded radially outer faces adjacentflanges 38 and have beveled or wedge-shaped inner edges to engagechamfers 30.

The compressive loads between member 38 and the cases are carriedthrough filler strips 42 and pass through the angle face 30. The lowerstrength ductile outer element is permitted by the use of the angularwedge to carry the compressive loads. The angle of the wedge may beselected for the appropriate relation between the tensile andcompressive loads and to the strengths of the material selected.

In this connection, the filler strips 42 are put into place after thecoupling member is lodged against the inner surface of the casingsection but before the flanges 38 have been deformed. As shown in FIG.3, the flanges 38 incline outwardly from the case as they extend awayfrom the web. It is possible to insert the filler strips 42 under theflanges by sliding them into place axially of the casing and rotatingthem under the flange or by sliding them in at the gap between the ends43 of the coupling ring as shown in FIG. 6.

FIG. 3 also illustrates a tool which may be employed for exerting aseparating force between the flanges and 38 to deform the flanges 38into tight contact with the filter strips 42. As shown, the tool 44,which may be referred to as a forming tool for convenience, comprises abody 46 defining ways 47 upon which heads 48 are reciprocable. The heads48 may be moved together or apart by a reverse threaded screw 50 havinga thrust bearing in a portion 51 of the body and in threaded engagementwith the heads 48. Screw 50 may be turned by a handle 52. Each head 48bears a forming roller 54 of proper contour to enter with a wedging andseparating action between the flanges 40 and 38. Forming rollers 54 arefreely rotatable on pintles 55 extending from the heads 48. As will beapparent, by advancing the heads 48 toward each other and traversing thetool 44 along the coupling member 15, the relatively thin section flange38 is deformed so as to bear positively against the filler strips 42 andhold the flanges 35 against the interior of the casing sections.

While it is possible to leave the outer portion of the coupling stripbeyond the flange 38 in place after the assembly has been completed, itis ordinarily desirable to remove it as a matter of reducing weight andpossible obstruction to other elements. This may readilybe done by amachining operation such as turning or grinding. The joint thus made isof a semi-permanent nature but may be separated without damage to thecasing sections by cutting off the flanges 38.

The coupling member 15 embodies another feature which may be desirablewhere the rings are used in hot environments, and particularly withdouble-walled structures. This is embodied in shield flanges 56extending from the inner edge of the web portion 31 and bearing againstthe inner surface of the casing sections. The shield flange shields thestructural flanges 35 to some extent from the hot motive fluid flowingthrough the turbine. A flange such as 56 may also be provided in somecases as a fairing or as means to improve the sealing ability of thecoupling with respect to leakage from the interior to the exterior ofthe casing or duct. The flanges 56 do not limit the outward movement ofthe coupling member into its seated position. They are spaced so as toallow full seating or may yield slightly to allow full seating. Notbeing a structural element, they need not be particularly rigid.

The coupling member 14 shown in FIG. 1 may be of the same general typeas the coupling member 15 just described except that it does not includethe additional shielding flange 56, nor does the web 31 extend inwardlyof the connecting flanges 35. It will be noted that the member 14 is ona steeply tapering portion of the casing and the same type of couplingmember can be used even though the casing surfaces joined are strictlyradial rather than axial or tapering.

FIG. 4 shows a modified form of the coupling member identified ascoupling member 58. This is of the same configuration in most respectsas the coupling member 15 of FIG. 2. However, it is applied in adifferent manner. In the installation shown in FIG. 4, the filler strips42 are omitted. Instead, flanges 59 which correspond to the flanges 38of FIG. 2 are deformed sharply toward each other and toward the casingsection, being rebent so that the margins of these flanges bear againstthe chamfered abutments 30 on the casing sections 11 and 12. This may beaccomplished by a swaging tool bearing rollers of the general formindicated at 54' in FIG. 4. Since the remainder of the casing joint isthe same as that previously described in detail with respect to FIG. 2,it will not be further described here. It should be apparent that inthis form, as in the form previously described, there is a part which isdeformed to hold the connecting flanges 35 against the casing sectionsand to bias the casing sections apart against the shoulders on theconnecting flanges.

Referring to FIG. 5, when the coupling member is in the form of a ringand is applied so that it is expanded outwardly into engagement with thecasing section, there will ordinarly be a gap between the ends of thecoupling ring when it is in place. The gap may be minimized by employinga segmented ring, but this is not preferred. The ends 43 of the ringpreferably are finished so as to be substantially parallel when the ringis expanded into place. With a large radius circle, this is inherent. Itwill be understood that FIG. 5 exaggerates the curvature of the ringwith respect to the usual installation. While various types of overlapof the ends of the strip might be employed, it is preferable to have theends cut off straight and to employ means to close the gap between theends so as to prevent leakage through the gap and also to provide ablock against movement of the ends of the ring toward each other. Themeans which I have devised for this purpose and prefer for closing thegap between the ends 43 of the coupling ring 15 is the key 60 shown inFIGS. 5 to 8. Key 60 may be an extrusion of steel and may be straightrather than curved for the usual application to where the circumferenceis large. The key may be made as a long strip from which a section ofdesired length for the particular installation is cut off or may beotherwise produced of a desired length. Key 60 comprises a central web62 terminating in a cross flange or head 63 similar to the head 39 ofthe coupling member. Two collapsible webs 64 extend back alongside theweb 62 from its edge opposite the head 63. Webs 64 terminate in beveledflanges 66 which, as will be apparent from FIG. 6, are configured to fitthe chamfered abutment 30 of the walls 11 and 12 to be joined. Thedevice in its initial form as illustrated in FIG. 7 may be insertedbetween the ends 43 of the coupling ring until the flanges 66 bottomagainst the abutments 30, whereupon the flanges 66 are held inengagement with the casing by a suitable tool while the head 63 ispulled outwardly to cause the webs 64 to collapse and fold out to formthe anchorage 67 shown in FIG. 6. The outer part of web 62 and the head63 may then be machined so that this part does not project any furtherthan the coupling ring or strip.

While I am aware that fasteners applying this mode of retention arecommercially available, I am not aware of any application of thisprinciple equivalent to that which is described here to complete acoupling ring or to serve as means for closing and sealing a gap in sucha ring.

The key 60 may, of course, also be used with the coupling strip 58 shownin FIG. 4.

FIGS. 8, 9, and illustrate a further feature which may be incorporatedin a casing joint according to my invention, such as that of FIG. 2, ananti-slip or anti-torque connection. FIGS. 8 and 9 are views similar toFIGS. 2 and 3 of a casing joint before and after deformation of thecoupling member or ring 75 corresponding to member 15. However, in theseviews the coupling ring is illustrated as omitting the shield flanges56, which may or may not be incorporated, depending upon therequirements of the particular installation.

Referring to the drawings, the coupling ring 75 includes flanges 76 tocooperate with flanges 27 of the casing sections, includes thedeformable or ductile flanges 77, and the outer ring or abutment 79,these being joined by a web as in the coupling ring previouslydescribed. In the structure illustrated in FIGS. 8 through 10, thecasing sections identified as 81 and 82 are formed for cooperation withthe casing joint as are the casing sections 16 and 19 previouslyreferred to, but have additionally a ring of teeth 84, the teeth 84projecting from the outer surface of each casing section. These teethmay be of any desired configuration and may be provided by cuttingnotches in low flanges on the exterior of the casing sections. Theductile flanges 77, when they are formed downwardly to engage the fillerstrips 42, are also forced into the interstices between teeth 84 so thatthe teeth 84 cut into the margins of the flanges 77, as indicated at 85in FIG. 10.

With this structure, a positive lock against relative rotation of thecasing sections about the axis of the sections or, generally, relativetranslation perpendicular to the plane of FIG. 8, is provided. This isin addition to the frictional restraint against such rotation which isprovided in structures omitting the lock.

The preceding description has had direct relation to use of the casingcoupling arrangement for circumferential joints in casings. While thereis likely to be less need for its use in joints which extend axially ofa casing or of shells of any sort, such axial split lines are known andthe coupling joint is obviously suited to use in such installations. Asa matter of fact, it may be easier to fit in an axially extending jointbecause there is not the matter of the gap between the ends whichseparate when the ring is fitted that there is when the ring is used asillustrated in FIG. 5.

It is also possible, although in most instances less convenient, to fiteither an axially extending or circumferentially extending joint insideout, so to speak, so that the abutments on the casing with which theshoulders of the coupling member engage are on the outer side of thecasing and the flange 38 or 59 of the coupling member is on the insideof the casing. This would have the advantage in connection withcircumferential joints that the gap in the coupling member would tend toclose as it is fitted into place and, therefore, there should be no needfor a key or other means to close the gap which results from opening upof the coupling ring in the type of installation shown in FIG. 5.However, it would ordinarily be less convenient to deform and machinethe coupling strip. Clearly,- FIGS. 2, 3 and 4 can apply equally well toan axial or circumferential joint, or to an inside or outside deformableflange.

It should be apparent to those skilled in the art that the practice ofmy invention will result in strong, secure and lightweight connectionsbetween members of a shell or casing of any sort which is readilyapplied, rattle free, and well sealed. Also, one which can, if desired,be removed without damage to any part other than the coupling ring orstrip itself which would have the deformable flanges machined away.

The detailed description of preferred embodiments of the invention forthe purpose of explaining the principles thereof is not to be consideredas limiting or restricting the invention, as many modifications may bemade by the exercise of skill in the art.

Iclaim:

l. A pressure vessel or the like comprising, in combination, two wallsections having juxtaposed edges and a coupling member positivelyjoining the edges of the sections, each section having a first abutmenton one surface adjacent to the edge and facing away from the othersection and having a second abutment forming part of the other surfaceadjacent to the edge and facing toward the other section, the couplingmember being a strip disposed between the edges of the wall sections anddefining two rigid shoulders, one shoulder engaging each first abutmentto hold the sections together, and defining two plastically deformableflanges, which are plastically deformed toward said other surfacethereby, cooperating with the second abutments to bias the sectionsapart and with the said other surface to retain theshoulders inengagement with the first abutments; the said flanges being sufficientlydeformable to allow clearance for entry of the abutments into engagementwith the shoulders before deformation of the flanges and to be deformedtoward the said other surface for retention of the coupling member.

2. A combination as recited in claim 1 in which the deformable flangesdirectly engage the second abutments.

3. A combination as recited in claim 1 including also filler stripsdisposed between the deformable flanges and the second abutments andloaded toward the second abutments by the deformable flanges.

4. A combination as recited in claim 1 in which the coupling memberincludes a portion defining a reaction surface for a tool adapted toengage and deform the deformable flanges.

5. A combination as recited in claim 1 in which the edges define aclosed curve and the coupling member is a split ring.

6, A combination as recited in claim 5 in which the first abutments areon the outer surface of the sections.

7. A combination as recited in claim 5 in which the first abutments areon the outer surface of the sections.

8. A combination as recited in claim 7 including also a key deformablefor retention disposed in the gap defined by the split in the ring tofill the gap.

9. A combination as recited in claim 1 in which the coupling member isformed of two metallic strips bonded together to form an integral strip,one strip being of a metal more ductile than the other.

10. A combination as recited in claim 1 in which the coupling member isformed of two metallic strips bonded together, one strip being of ametal more resistant to high temperature than the other.

11. A structure comprising, in combination, first and second plateshaving generally coplanar edges juxtaposed along a split line andcoupling means at the split line positively connecting the plates so asto withstand forces tending to separate the plates and so as to preservethe alignment of the plates, each plate having a rigid flange extendingfrom one of the surfaces of the plate defining an abutment adjacent toand facing away from the split line, the coupling means including astrip disposed between the edges of the plate and having two rigidmutually aligned flanges each defining a shoulder engaging one of theabutments on the plates so that the interengaging abutments andshoulders positively restrain the plates against separation, thecoupling means also including securing means bearing against the surfaceof the plates opposite to the said flanges holding the shoulders inengagement with the abutments, the securing means including meansintegral with the strip sufficiently plastically deformable toward theplates to allow clearance for entry of the abutments into engagementwith the shoulders before deformation and deformed plastically towardthe plates thereby pressing the securing means against the plates.

12. A combination as recited in claim 11 in which the edges define aclosed curve and the strip is in the form of a split ring.

13. A combination as recited in claim 12in which the ring is segmented.

14. A combination as recited in claim 12 in which the abutments are onthe inner surface of the plates.

15. A combination as recited in claim 11 in which the plasticallydeformable means loads the plates in a sense to separate the edges.

16. A combination as recited in claim 15 including also filler stripsdisposed between the deformable means and the plates.

17. A combination as recited in claim 11 in which the plasticallydeformable means is defined by flanges extending from the strip.

18. A combination as recited in claim 17 in which the coupling meansdefines flanges extending from the strip over the deformable means toprovide a reaction surface for a tool adapted to deform the deformablemeans.

19. A combination as recited in claim 11 in which one surface of thestructure is exposed to hot fluid, the portion of the strip defining theshoulders being toward the surface of the structure exposed to the hotfluid and the securing means being on the other surface, the flangesdefining the shoulders being of a material more highly resistant totemperature than the plastically deformable means.

20. A combination as recited in claim 19 including also a heat shieldengaging the surface of the casing and shielding the flanges definingthe shoulders from the hot fluid.

21. A combination as recited in claim 20 in which the heat shield is anintegral part of the strip.

22. A wall comprising, in combination, two wall sections having edgesjuxtaposed; and a coupling member rigidly connecting the sections, thecoupling member being a unitary structure including a web, rigid firstflanges extending laterally from both faces of the web and includingshoulders interlocking with the wall sections, the wall sections havingabutments on one surface interlocking with the shoulders, second flangesextending laterally from both faces of the web in position to overliethe other surface of the wall sections, the second flanges being of amaterial plastically deformable toward the casing sections to hold thecoupling member interlocked with the wall sections, and third flangesextending laterally from both faces of the web more remote from the wallthan the second flanges, the third flanges providing a reaction surfacefor a tool to deform the second flanges toward the casing.

23. A combination as recited in claim 22 in which the edges define aclosed curve and the coupling member is a split ring.

24. A combination as recited in claim 22 in which the said abutments aredisposed in a recess below the corresponding surface of the wall, and inwhich the coupling member includes fourth flanges extending from the webinto contact with the wall to shield the first flanges from directimpingement by fluid contained by the wall.

25. A combination as recited in claim 24 in which the coupling member isa composite of two sections bonded together, a first section definingthe first and fourth flanges and a portion of the web, and a secondsection defining the remainder of the coupling member.

26. A combination as recited in claim 25 in which the first section isselected for resistance to high temperature and the second is selectedfor ductility.

27. A combination as recited in claim 26 in which the edges define aclosed curve and the coupling member is a split ring.

28. A combination as recited in cla1m 22 lncluding also fi er stripsdisposed between the deformable flanges and the wall sections and loadedagainst the surface of the wall sections by the deformable flanges.

29. A combination as recited in claim 1 including also an anti-slipconnection between the wall sections defined by teeth extending from thewall sections and by the deformable flanges, the deformable flangesbeing engaged with the said teeth.

mg UNITED STATES PATENT OFFHCE CERHFICATE @F CORRETE@N Patent No. 3Dated April 11, 1972 Ihventonls) Douglas Johnson It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 3,, line 8, delete "position, and substitute to line 10', after"parts" ineert are Column 6, line 52,, delete "outer" and substituteinner P Signed and sealed this 22nd day of August 1972.

(SEAL) Attest:

EDWARD ILFLETCHERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner ofPatents

1. A pressure vessel or the like comprising, in combination, two wallsections having juxtaposed edges and a coupling member positivelyjoining the edges of the sections, each section having a first abutmenton one surface adjacent to the edge and facing away from the othersection and having a second abutment forming part of the other surfaceadjacent to the edge and facing toward the other section, the couplingmember being a strip disposed between the edges of the wall sections anddefining two rigid shoulders, one shoulder engaging each first abutmentto hold the sections together, and defining two plastically deformableflanges, which are plastically deformed toward said other surfacethereby, cooperating with the second abutments to bias the sectionsapart and with the said other surface to retain the shoulders inengagement with the first abutments; the said flanges being sufficientlydeformable to allow clearance for entry of the abutments into engagementwith the shoulders before deformation of the flanges and to be deformedtoward the said other surface for retention of the coupling member.
 2. Acombination as recited in claim 1 in which the deformable flangesdirectly engage the second abutments.
 3. A combination as recited inclaim 1 including also filler strips disposed between the deformableflanges and the second abutments and loaded toward the second abutmentsby the deformable flanges.
 4. A combination as recited in claim 1 inwhich the coupling member includes a portion defining a reaction surfacefor a tool adapted to engage and deform the deformable flanges.
 5. Acombination as recited in claim 1 in which the edges define a closedcurve and the coupling member is a split ring.
 6. A combination asrecited in claim 5 in which the first abutments are on the outer surfaceof the sections.
 7. A combination as recited in claim 5 in which thefirst abutments are on the outer surface of the sections.
 8. Acombination as recited in claim 7 including also a key deformable forretention disposed in the gap defined by the split in the ring to fillthe gap.
 9. A combination as recited in claim 1 in which the couplingmember is formed of two metallic strips bonded together to form anintegral strip, one strip being of a metal more ductile than the other.10. A combination as recited in claim 1 in which the coupling member isformed of two metallic strips bonded together, one strip being of ametal more resistant to high temperature than the other.
 11. A structurecomprising, in combination, first and second plates having generallycoplanar edges juxtaposed along a split line and coupling means at thesplit line positively connecting the plates so as to withstand forcestending to separate the plates and so as to preserve the alignment ofthe plates, each plate having a rigid flange extending from one of thesurfaces of the plate defining an abutment adjacent to and facing awayfrom the split line, the coupling means including a strip disposedbetween the edges of the plate and having two rigid mutually alignedflanges each defining a shoulder engaging one of the abutments on theplates so that the interengaging abutments and shoulders positivelyrestrain the plates against separation, the coupling means alsoincluding securing means bearing against the surface of the platesopposite to the said flanges holding the shoulders in engagement withthe abutments, the securing means including means integral with thestrip sufficiently plastically deformable toward the plates to allowclearance for entry of the abutments into engagement with the shouldersbefore deformation and deformed plastically toward the plates therebypressing the securing means against the plates.
 12. A combination asrecited in claim 11 in which the edges define a closed curve and thestrip is in the form of a split ring.
 13. A combination as reciteD inclaim 12 in which the ring is segmented.
 14. A combination as recited inclaim 12 in which the abutments are on the inner surface of the plates.15. A combination as recited in claim 11 in which the plasticallydeformable means loads the plates in a sense to separate the edges. 16.A combination as recited in claim 15 including also filler stripsdisposed between the deformable means and the plates.
 17. A combinationas recited in claim 11 in which the plastically deformable means isdefined by flanges extending from the strip.
 18. A combination asrecited in claim 17 in which the coupling means defines flangesextending from the strip over the deformable means to provide a reactionsurface for a tool adapted to deform the deformable means.
 19. Acombination as recited in claim 11 in which one surface of the structureis exposed to hot fluid, the portion of the strip defining the shouldersbeing toward the surface of the structure exposed to the hot fluid andthe securing means being on the other surface, the flanges defining theshoulders being of a material more highly resistant to temperature thanthe plastically deformable means.
 20. A combination as recited in claim19 including also a heat shield engaging the surface of the casing andshielding the flanges defining the shoulders from the hot fluid.
 21. Acombination as recited in claim 20 in which the heat shield is anintegral part of the strip.
 22. A wall comprising, in combination, twowall sections having edges juxtaposed; and a coupling member rigidlyconnecting the sections, the coupling member being a unitary structureincluding a web, rigid first flanges extending laterally from both facesof the web and including shoulders interlocking with the wall sections,the wall sections having abutments on one surface interlocking with theshoulders, second flanges extending laterally from both faces of the webin position to overlie the other surface of the wall sections, thesecond flanges being of a material plastically deformable toward thecasing sections to hold the coupling member interlocked with the wallsections, and third flanges extending laterally from both faces of theweb more remote from the wall than the second flanges, the third flangesproviding a reaction surface for a tool to deform the second flangestoward the casing.
 23. A combination as recited in claim 22 in which theedges define a closed curve and the coupling member is a split ring. 24.A combination as recited in claim 22 in which the said abutments aredisposed in a recess below the corresponding surface of the wall, and inwhich the coupling member includes fourth flanges extending from the webinto contact with the wall to shield the first flanges from directimpingement by fluid contained by the wall.
 25. A combination as recitedin claim 24 in which the coupling member is a composite of two sectionsbonded together, a first section defining the first and fourth flangesand a portion of the web, and a second section defining the remainder ofthe coupling member.
 26. A combination as recited in claim 25 in whichthe first section is selected for resistance to high temperature and thesecond is selected for ductility.
 27. A combination as recited in claim26 in which the edges define a closed curve and the coupling member is asplit ring.
 28. A combination as recited in claim 22 including alsofiller strips disposed between the deformable flanges and the wallsections and loaded against the surface of the wall sections by thedeformable flanges.
 29. A combination as recited in claim 1 includingalso an anti-slip connection between the wall sections defined by teethextending from the wall sections and by the deformable flanges, thedeformable flanges being engaged with the said teeth.